1. Field of the Invention
The present invention relates to wound-dressing materials and methods for manufacturing the same. Specifically, the present invention relates to wound-dressing materials suitable for healing the wounds such as traumas, burns, frostbites, ulcers, and bedsores.
2. Description of the Related Art
Recently, in treatment of traumatic skin lesions such as traumas, burns, frostbites, ulcers, and bedsores, formation of granulation tissue has been enhanced by using wound-dressing materials for keeping environments of wound surfaces moist to regenerate normal skins at the wound sites. In the present commercially available wound-dressing materials, a wide variety of raw materials, i.e. animal-derived materials such as chitin, synthetic materials, and plant-derived materials such as alginic acid, are used. Compositions of each wound-dressing material are determined depending on subjects to be healed. Namely, the wound-dressing material is determined in consideration of the conditions of the wound and the characteristics of the wound-dressing material.
Examples of ingredients of the wound-dressing materials include animal-derived materials such as chitin and chitosan. Chitin and chitosan are natural polysaccharide macromolecules, and have biocompatibility, degradable properties, and low toxicity. Therefore, the wound-dressing materials made of these materials have biocompatibility effective to traumas such as burns. Chitin and chitosan are also used for other purposes than for the wound-dressing materials. Yaizu Suisankagaku Industry Co., Ltd. produces low-molecular chitin and chitosan as a sweetener for functional foods (Japanese Unexamined Patent Application Publication No. 2000-281696) and chitosan as a food additive (trade name: ChitoClear) having antimicrobial properties. Snow Brand Milk Products Co., Ltd. uses chitosan as a stabilizer for foods such as Dole fruits and cheesecake.
Chitin and chitosan are different from each other in the following points. Structurally, chitin is synonymous with chitosan having an acetylated amino group, characteristically, chitin is insoluble in acids, alkalis, and organic solvents that are commonly used, but chitosan is soluble in dilute hydrochloric acid and dilute acetic acid. Beschitin (registered trademark No. 2130021) is a sheet-type chitin-derived wound-dressing material. Since the dressing material containing chitin has biocompatibility, it is effective to traumas such as burns. Besides chitin, a cellophane-like membrane having a high organic affinity and adhesion is formed by thinly spreading a chitosan solution and drying it. It has been confirmed that the chitosan membrane has antibacterial properties and is superior in healing of sores, absorption of exudates, and flexibility [Tachihara, K., Onishi, H., Machida, Y., et al., Evaluation of membranes of chitin, chitosan, and a chitin-chitosan mixture as a burn-dressing material, Yakuzaigaku (Pharmacology), 1997, 57(1), 40-49; Tachihara, K., Onishi, H., Machida, Y., et al., Preparation of silver sulfadiazine-containing sponge membranes of chitosan and a chitin-chitosan mixture and their evaluation as burn-dressing materials, Yakuzaigaku (Pharmacology), 1997, 57(3), 159-167].
It is known that dressing materials of polymers are more effective to chronic wounds. Chronic wounds are defined as wounds that are not sufficiently repaired by a normal mechanism, and are typical phenomena caused by basic disorders such as diabetes, vascular disease, and circulatory disorders in bedridden patients. Therefore, the chronic wounds are classified into bedsores (decubitus), venous ulcers, and diabetic ulcers according to the basic disorders that cause the chronic wounds. Various types of treatments and materials are used according to the causes of disorders in order to deal with various types of disorders and to enhance the healing of wounds. In healing of the chronic wounds that are difficult to be healed, it is known that dressing materials of chitosan polymers having characteristics of providing moist environment for the wounds are more effective than absorptive gauze mainly used in conventional treatment.
Recently, the healing of relatively mild wounds such as burns and traumas have been remarkably developed, and various dressing materials and methods for the healing have been studied. The materials are mainly classified into synthetic materials and biomaterials. Examples of the synthetic materials include polyurethane films, for example, Tegaderm (3M Health Care, Ltd.), Opsite Wound (Smith & Nephew plc.), IV3000 (Smith & Nephew plc.), and Bioclusive (Johnson & Johnson Co.,); polyurethane forms, for example, Hydrosite (Smith & Nephew plc.); and hydrocolloids, for example, DuoActive (Convatec Co.), Comfeel (Coloplast Co.), Tegasorb (3M Health Care, Ltd.), and Absocure (Nitto Medical Corp.). Examples of the biomaterials include alginate dressing materials made of alginic acid, for example, KaltoStat (Convatec Co.), Sorbsan (Alcare Company), Algoderm (Medicon, Inc.), and Kurabio AG (Kuraray Co., Ltd.); and chitin fiber sheets, for example, Beschitin (Unitika).
Leaves of kumazasa (scientific name: Sasa albomarginata or Sasa veitchii, Genus: Sasa, Family: Gramineae) are widely used as wrapping materials of foods because of antibacterial and antiseptic effects thereof. Various activities including antiulcer effects, antitumor effects, anti-inflammatory effects, sedating effects, detoxification effects, and diuretic effects are confirmed by pharmacological studies. Additionally, it has been recently reported that Kumazasa extract produced by Hoshi Seiyaku K. K. has antiulcer effects against stress ulcers, pylorus ligation ulcers (ulcers caused by gastric acid), and drug-induced ulcers due to aspirin, caffeine, or the like. Antitumor effects and cell repair-enhancing effects are also reported. Furthermore, kumazasa extract is directly applied to burn and wound sites with the intention to utilize the activities for regeneration of epithelial and muscular tissues and the antiseptic and antitumor effects. The effects of this are confirmed.